It is known that for a portion of the duty cycle of a typical multiple-cylinder internal combustion engine, the load can be met by a functionally smaller engine having fewer firing cylinders, and that at low-demand times fuel efficiency can be improved if one or more cylinders of a larger engine can be withdrawn from firing service. It is known in the art to accomplish this by de-activating a portion of the valve train associated with pre-selected cylinders in any of various ways. For example, a special cam finger follower having a latching pin or slide which may be actuated and/or deactuated hydraulically. The cam finger follower is so configured that it causes low or no lift of the valve when the pin is disengaged and high lift of the valve when the pin is engaged.
Various methods and apparatus for actuating this type of latching pin or slide are known. For example, U.S. patent application Publication No. U.S. 2003/0200947 A1 discloses a hydraulic apparatus and return spring for latching and delatching a latching pin of a deactivating roller finger follower. The latching pin is disposed in, and extends from, a bore in an outer finger arm which is supported by a hydraulic lash adjuster. When moved inwards of the outer finger arm, the pin engages a central slider member which follows the surface of a camshaft lobe. When valve deactivation is desired, engine oil pressure supplied to the apparatus is increased to a level sufficient to overcome the force of the return spring and move the latching pin out of engagement with the slider member. The slider member continues to follow the surface of the camshaft, but the cam motion is not translated to the outer finger arm, and the valve is not actuated thereby.
For another example, a special hydraulic valve lifter having radially-operative latching pins also may be actuated or deactuated hydraulically. When the lifter is deactuated by high-pressure oil overcoming a latching spring, a pushrod seat is disengaged to deactivate the associated engine valve, while the cam-follower portion continues to follow the cam lobe in lost motion.
In providing such actuation mechanisms, it can be advantageous to provide ordinary engine oil as the pressurized actuating medium, supplied conventionally from the main engine oil pump via a standard engine oil gallery with minimal special oil porting. Further, it is advantageous to be able to throttle the flow of oil between high-flow/high-pressure and low flow/low-pressure without ever completely shutting off the flow of oil, as is the case in prior art on/off solenoid-actuated spool valves.
It is a principal object of the present invention to controllably vary the flow of pressurized oil between a high-flow/high-pressure condition and a low flow/low-pressure condition.
It is a further object of the invention to provide such control electromechanically via a simple solenoid valve.